Filter medium for removing hydrogen cyanide from tobacco smoke



United States Patent 3,410,282 FILTER MEDIUM FOR REMOVING HYDROGENCYANIDE FROM TOBACCO SMOKE Theodore Roosevelt Walker and John EdwardKiefer,

Kingsport, Tenn., assignors to Eastman Kodak Company, Rochester, N .Y.,a corporation of New Jersey No Drawing. Filed Mar. 13, 1967, Ser. No.622,470 6 Claims. (Cl. 131267) ABSTRACT OF THE DISCLOSURE Tobacco smokefiltering mediums containing at least one amine salt for selectivityremoving hydrogen cyanide from tobacco smoke. The particular salts areproduced by reacting a primary alkyl or hydroxyalkyl amine conta ning nomore than 8 carbon atoms with a carboxylic acid.

It has been known for some time that tobacco smoke contains certainharmful components including hydrogen cyanide which, for obviousreasons, should be removed from tobacco smoke. It is well known, forexample, that hydrogen cyanide is an extremely harmful ciliatoxiccompound which contributes nothing beneficial to the pleasant taste oraroma of the smoke or to the smoker. It has therefore been the desire ofthe tobacco industry to provide an effective and practical tobacco smokefilter which is capable of selectively removing hydrogen cyanide fromcigarette smoke without at the same time adversely affecting thepleasant taste and aroma found in the smoke.

The search for a suitable yet inexpensive filtermg medium which could beused with any tobacco product, and especially with cigarettes, led tothe development of the so-called fibrous filter unit. These fibrousfilters, and particularly those made of cellulose acetate tow, have beenfound to be very effective for removing solid particulate mattercommonly referred to as tar from tobacco smoke. However, it isdifiicult, if not impossible, to remove certain undesirable components,such as hydrogen cyanide, which is found in tobacco smoke by use of suchfilters.

It has been known that certain gas adsorbing additives in the form offinely divided particles can be dispersed within the fibrous filter forremoving such undesirable gases. These particles of solid materials weregenerally placed on the surface of a fibrous material in either a dry orliquid state. Numerous solid adsorbing materials were tried withactivated carbon and certain silica gels being the ones most often used.

However, there are certain limitations and disadvantages to usingactivated carbon in a cigarette filter for removing cigarette smokevapors. Activated carbon does not remove cigarette smoke vaporselectively even though it has more afifinity for some vapor componentsthan others. In general, the adsorption of vapors by carbon is dependentupon the boiling point of the. vapor being adsorbed, that is, the leastvolatile vapors will be more readily adsorbed and retained by activatedcarbon addltives as opposed to the more volatile vapors. Th1s IS adefinite disadvantage since several of the least volatile vapors incigarette smoke are those which give flavor and taste to the smoke andare neither deleterious nor harmful to the smoker. Therefore, theremoval of these vapors Patented Nov. 12, 1968 ICC is highly undesirableand if permitted to occur can result in what has commonly been referredto as a carbon or dry taste.

The adsorption of vapors by carbon in a cigarette filter therefore is aphysical phenomenon dependent upon temperature and pressure. Since thetemperature of a cigarette filter increases as the burning zone of thecigarette approaches the filter during the smoking of a cigarette, thetemperature of the carbon in the filter is raised causing the morevolatile vapors adsorbed on the carbon to be eluted from the carbon.Thus, the carbon particles do not remove the more volatile vaporselfectively. In addition, as stated above, the less volatile gases whichcontribute to the taste and aroma of the smoke, and are generallyneither deleterious or harmful, are also removed by carbon filters.Furthermore, since the removal of solid particulate matter commonlycalled tar is also of prime importance, cigarette filters containingactivated carbon additives for the removal of vapors do not fulfill therequirement for the removal of solid particulate matter such as tar.Thus the problem of the tobacco industry; namely, how to economicallyproduce a filter which is capable of selectively removing vapors such ashydrogen cyanide from the vapor phase of tobacco smoke, has todateremained unsolved.

It has been reported that certain amines when applied to cigarettefilters remove noxious gases from the smoke more selectively thancarbon; however, there are several decided disadvantages to their use infilters. For example, amines are notorious for their offensive odors andthis property alone eliminates most of them from consideration Anotherdisconcerting property of amines is their strong basicity which causesskin irritation; therefore if they are to be used in cigarette filters,they must be prevented from entering the smoke stream. Amine filtersalso tend to impart an off-taste to the smoke which may be due to theimbalance caused by absorption of acids by the amine. Furthermore, theycannot be used as additives to cellulose acetate, the most widely usedfilter medium, because they degrade it.

According to this invention it has been found that the aforementioneddifficulties of the prior art tobacco smoke filters can be substantiallyovercome by the use of an amine salt of a carboxylic acid dispersed on acarrier inserted into a stream of tobacco smoke and arranged to provideinterstices for the passage of smoke therethrough, serves to selectivelyremove hydrogen cyanide from the smoke. These carboxylic acid salts areprepared by reacting primary or secondary alkyl and hydroxyalkylaminescontaining no more than 8 carbon atoms with an acid. Some amines whichhave been found particularly eifective are: ethylamine, dibutylamine,2-amino-2-methyl-l-propanol, ethanolamine, and diethanolamine. The acidsused in the preparation of the salts can be mono-, di-, tri-, andtetracarboxylic acids which include the following: carbonic, acetic,itaconic, lactic, succinic, citric, and pyromellitic acids.

As will be apparent, filters incorporating these amine salts of acarboxylic acid provide a means for selectively removing hydrogencyanide from cigarette smoke vapors without the use of activatedcarbons, silica gel, molecular sieve or other materials commonly usedfor the physical adsorption of vapor. It has been found that such acidsalts are capable of chemically reacting on contact with the hydrogencyanide vapor to neutralize the vapor thereby assuring that cyanide isnot later released or otherwise eluted from the filter due to theincrease in temperature of the filter during the smoking of thecigarette. Furthermore, such means employed for selectively removinghydrogen cyanide from the vapor phase of tobacco smoke does so withoutdecreasing the capacity of the filter for removing solid particulatematter such as tar from the tobacco smoke. Since the additive for thefilter element is an odorless, nonvolatile, nonirritant which can beapplied to such materials as cellulose acetate without subsequentdegradation of the material, it can be used freely without fear of itsaffecting the taste of the tobacco smoke or entering the smoke stream.

The carboxylic acid salts of certain alkyl or hydroxyalkylamines may beapplied by sifting, dusting, shaking, or from a plasticizer dispersionsuch as glyceryl triacetate. It may also be applied from any othersuitable liquid by any convenient method such as by spraying or rollingon the carrier filter medium. Furthermore, more than one salt may beused as a mixture if desired. The fibrous media upon which the additivesof this invention may be used is preferably a crimped continuousfilament cellulose acetate tow, preferably of a denier per filament ofabout 1.620. However, it will be appreciated that such salts may beequally effectively employed upon filters which are made from other basematerials such as paper, cotton, propylene and polyethylene fibers, orany other suitable material that can be formed into tobaco smokefilters.

The carboxylic acid salts of aliphatic amines may be applied to thepaper, tow or other carrier materials in the amount of from about 10-150mg. (milligrams) per filter, the preferred amount being about 20 to 60mg. By uniform application to the surface of the fibrous media the saltis enabled to take advantage of the large surface area which providesthe contact necesary for effective hydrogen cyanide removal.

It also has been found that it is possible to produce a fibrousfiltering unit which is capable of selectively removing hydrogen cyanidefrom a gaseous medium by spinning the fibers of the filter from a dopeof cellulose acetate which contains an additive of the water-soluble,organic salts. Since these organic salts are embedded in the celluloseacetate fibers as the fibers are being spun, the necessity of includingadditional processing steps, materials and equipment into themanufacturing operation is alleviated. The selected Water-soluble salts,if properly prepared, can be mixed with selective types of celluloseacetate dopes and spun to give a filament that readily neutralizes thehydrogen cyanide in tobacco smoke. It has been found, for example,rather unexpectedly that the salts are not masked by the acetate to adegree which would prevent their etfective removal of hydrogen cyanidewhen employed in tobacco smoke filters.

The spinning solution or dope from which the filaments containing theorganic salt are spun can be produced in any one of several manners. Inits broadest aspect, this can be accomplished by adding directly to thecellulose acetate solution one or more of the carboxylic acid saltsselected from the groups that are prepared from primary or secondaryalkyl and hydroxyalkylamines which contain no more than 8 carbon atomswhich are reacted with a suitable acid. More specifically, these saltsare added to an acetone solution of cellulose acetone solution ofcellulose acetate in the amount of from about to 30 percent based onweight of the cellulose acetate. After the carboxylic acid salts havebeen added to the acetone solution of cellulose acetate, the mix isuniformly dispersed. The spinning solution containing the carboxylicacid salt is now ready to be spun into filaments on a conventionalspinning machine after which it can be formed into a tobacco smokefilter by any suitable manner.

The subject mater which is regarded as the invention is clearly pointedout and distinctly claimed in the concluding portion of thespecification. The invention, however, as to its organization andoperation, together with the further objects and advantages thereof willbest be understood by reference to the following examples which arepreferred embodiments of our invention.

EXAMPLE I With methanol as sol-vent, a solution of ethanol ammoniumcitrate was prepared by adding a ratio of three moles ethanolamine toone mole of citric acid. The solution was added to commercialcreped-paper filters and after evaporation of the methanol, the 10 mm.filters each contained 60 mg. of the salt.

They were attached to king size cigarettes and the cigaretes smoked byan automatic smoking device which removed particulate matter from thesmoke by means of a Cambridge filter. By a colorimetric test the smokevapors were shown to contain 76% less HCN than vapors from an unfilteredcigarette smoked in the same manner.

In addition ciliatoxicity of the vapor phase of smoke from thesefiltered cigaretes was determined by the method which was described bySpears, Tryfiates, and Schultz at the 18th Tobacco Chemists ResearchConference (1964) [see Science, 153, No. 3741, 1248 (1966)]. This methoduses clam gill cilia as the test specimen. This test showed that thefilter reduced ciliastasis of the gas phase of smoke by 80%.

EXAMPLE II An aqueous solution of dibutylamine was titrated toneutrality with 5% aqueous acetic acid. The resulting salt solution waspipetted onto 10 mm. cellulose acetate filters such that each filtercontained 60 mg. of the salt. When the filters were dry they were testedas in Example I. The elfect of this filter on the ciliatoxicity oftobacco smoke and its ability to remove HCN is shown in Table 1.

EXAMPLE III Diethanol ammonium carbonate was prepared by adding 50 mg.diethanolamine in CH OH to a 20 mm. cellulose acetate filter and passingCO through the filter for twenty minutes. The filters were attached tocigarettes and tested as in Example I with the results being given inTable 1.

EXAMPLE IV Seven hundred grams (3 /3 moles) of citric acid was addedslowly with mechanical stirring to a solution of ml. water in 1051 g.(10 moles) diethanolamine. An ice bath kept the temperature from risingabove 50 C. The pH of this preparation was 7.3 measured as a 5% aqueoussolution. Since diethanol ammonium citrate is a liquid, it was rolledonto cellulose acetate tow by a method'developed for the application ofplasticizers. The effect of this filter on the ciliatoxicity of tobaccosmoke and its ability to remove HCN is shown in Table 1.

EXAMPLE V Diethanol ammonium acetate, ethyl ammonium itaconate,1,1-dimethyl ethanol ammonium malonate, ethyl ammonium pyromellitate anddiethyl ammonium lactate were prepared as in Example I in a ratio of oneamino group per carboxyi group. Crimped cellulose acetate tow was spreadout to a length of approximately 15 in. The tow was sprayed with a 50-50w./w.% aqueous solution of the salt and dried. The tow was then sprayedwith triacetin, compacted, wrapped with a paper tape to form a rod andallowed to stand until firm. The triacetin cures the tow making a rigidrod and leaving the salt evenly distributed throughout the tow. Afterthe rod became firm it was cut to a 20 mm. length and attached to acigarette for testing as in Example I with the results being given inTable 1.

TABLE 1 Mg. Filter Inhibition of HCN Filter Additive Additive MediumCilia Fre- Removal quency percent percent Ethanol ammonium citrate 62Paper 5 76 Dibutyl ammonium acetate 60 Cellulose acetate. 0 85 Diethanolammonium carbonate 74 d 8 89 Diethanol ammonium citrate 78 3 82 Ethylammonium itaconate 65 10 82 1,1-dimethyl ethanol ammonium malonat 71 1279 Ethyl ammonium pyromellitate 78 8 85 Diethanol ammonium acetate 68 490 Diethyl ammonium lactate 65 8 80 None 0 Paper 62 0 Do 0 Celluloseacetate 58 0 Dom. 0 one 65 0 Carbon 113 Cellulose acetate 35 55 From theforegoing description and illustrative eX- 15 being produced by reactingan amine selected from the amples it is apparent the inventive conceptof incorporating certain amine salts of organic acids with the fibrouscarrier media of a tobacco smoke filter offers numerous de-toxicatingadvantages over those filters previously used in the tobacco industry.For example, a filter so produced is a highly selective one which iscapable of removing substantial amounts of the solid particulate matter,such as tar, found in tobacco smoke as the smoke moves through theinterstices of the filter, while at the same time selectively removinghydrogen cyanide from the vapor phase of the tobacco smoke byneutralizing or reducing it to a solid by-product which cannot later beeluted from the filter. Furthermore, the fact that the salt particlesmay also be embedded within the cellulose filaments of the filtereliminates sifting out and companion problems that have been heretoforepresent in filters containing solid additives. Furthermore, these aminesalts may be incorporated in any of the known filter fibrous media usedin the making of tobacco smoke filters such as, for example, celluloseacetate or paper. Thus, the hereinabove described method for theselective removal of hydrogen cyanide from the vaporous phase of tobaccosmoke has been found to be both surprising and effective in its abilityto remove this highly undesirable component from tobacco smoke and stillprovide the tobacco smoke with a taste and aroma most desirable for theultimate smoker.

What is claimed and desired to be secured by the United States LettersPatent is:

1. A tobacco smoke filter element adapted for selective removal ofdeleterious and noxious materials from tobacco smoke which comprises acarrier medium having as an additive thereon at least one amine salt,said salt group consisting of primary alkyl amines and hydroxyalkylamines containing no more than 8 carbon atoms with a carboxylic acid.

2. A tobacco smoke filter according to claim 1 in which the carboxylicacid is an acid selected from the group consisting of mono-, di-, tri-,or tetracarboxylic acids.

3. A tobacco smoke filter of claim 1 wherein the amine is selected fromthe group consisting of ethylamine, 2- amino 2 methyl 1 propanol,ethanolamine, and diethanolamine.

4. A tobacco smoke filter of claim 2 wherein the carboxylic acid isselected from the group consisting of carbonic, acetic, lactic, malonic,itaconic, succinic, citric, and pyromellitic acids.

5. The tobacco smoke filter element of claim 1 wherein the filterelement contains from about 10-150 mg. of

, said salt per filter element.

6. The tobacco smoke filter element of claim 1 wherein the carriermedium is selected from the group consisting of paper, cotton, celluloseacetate, polypropylene and polyethylene.

References Cited UNITED STATES PATENTS 2,920,416 1/1960 Kinnavy 131-266X 2,956,329 10/1960 Touey 131-266 X 2,968,306 1/1961 Touey et al 1312663,127,901 4/ 1964 Whitefield et al 131267 3,144,024 8/1964 Eichwald etal. 131-267 3,246,655 4/1966 Spears et al 131--266 X SAMUEL KOREN,Primary Examiner.

DENNIS J. DONOHUE, Assistant Examiner.

